In operating a fuel cell, generally, a temperature distribution is very critical design factor. In particular, a planar temperature distribution of an electrode is an important factor considered in determining a configuration of a gas flow channel, a composition of a supply gas, a flow rate, a position of a catalyst, a shape of a separator, and the like, in designing a fuel cell.
Conventionally, in order to measure a planar temperature distribution of a fuel cell electrode, a thermocouple made of a metal is directly attached to a certain portion of the fuel cell or inserted between the electrode and the separator.
However, in the related art measurement method, since the thermocouple is directly connected to a measurement spot (or portion) of a fuel cell, increasing a possibility of damaging the fuel cell and the thermocouple. Also, since the thermocouple made of a metal is used, electricity generated in the fuel cell may be leaked to outside through the thermocouple or electricity flows to a different electrode.
The leakage of electricity and/or electrical conduction o a different electrode causes many problems such as a degradation of performance, a reduction in lifespan, a safety accident, a system stop, and the like, of the fuel cell,
In addition, in terms of the characteristics of a fuel cell formed by stacking a plurality of electrodes, it is structurally difficult to measure a planar temperature distribution of a particular electrode. For example, in case of a molten carbonate fuel cell as a high temperature fuel cell, a thermocouple made of a metal is inserted into a portion of a separator to measure a temperature of an electrode. This measurement method, however, may cause leakage of electricity generated by the fuel cell through the thermocouple, and since the thermocouple made of a metal is exposed to electrolyte that corrodes the thermocouple, when the fuel cell is operated for 10,000 hours, the thermocouple is entirely short-circuited, and thus, it cannot be used any longer.